Sensitive pressure switch



Nov. 27, 1956 R. K. HIGGINS 2,772,330

SENSITIVE PRESSURE SWITCH Filed Nov. 17, 1952 FIG. I

7 mr.\\\ 3 Ill/4e /A\\\\\\\\\\\ llll/lmllll INVENTOR ROGER K. HIGGINS BY XKQM ATTORN United States Patent SENSITIVE PRESSURE SWITCH Roger K. Higgins, Takoma Park, Md., assignor to the United States of America as represented by the Secretary of the Navy Application November 17, 1952, Serial No. 320,968

1 Claim. (Cl. 200-83) This invention relates to a sensitive pressure switch and particularly to a pressure switch that is readily responsive to the pressures of shock waves such as those produced by the detonation of an explosive charge.

In the investigation of shock wave propagation, it is the usual practice to place sensitive-pressure switches at varying distances and locations with respect to the source of the shock waves. In order to obtain true measurements, the switch that is to be used must be sensitive to very low pressures, insensitive to static or atmospheric pressures, thermally invulnerable, and capable of providing a quick response. Heretofore, pressure switches having all of these characteristics were non-existent.

Therefore, it is an object of the present invention to provide a pressure switch that is capable of quickly responding to very low pressures such as those composing shock waves but is insensitive to static or atmospheric pressures.

Another object of this invention is to provide a pressure switch that is not materially injured when subjected to high temperatures.

A further object of this invention is to provide a pressure switch having the above-mentioned characteristics and which, in addition, is simple to construct and assemble.

Still further objects and attendant advantages will become evident from the following detailed description made in conjunction with the accompanying drawings, wherein:

Fig. 1 is a plan view of a pressure switch embodying this invention;

Fig. 2 is a section on line 2-2 of Fig. 1;

Fig. 3 is a section on line 33 of Fig. 1; and

Fig. 4 is a perspective view of the switch shown in Fig. 1.

Referring now to the drawings and in particular to Fig. 1, there is illustrated a sensitive pressure switch generally comprised of a plate 11 of rigid material having a central aperture 12 therein and a disk 13 of insulation material loosely positioned in said aperture. Adjacent to and on diametrically opposite sides of the aperture 12, there are disposed two electrical contact terminals 14 and 15, each of which is constructed wih a flat contact surface 16 and a terminal post 17. The contact terminals, 14 and 15, are secured, as by nuts 18 and bolts 19, to the plate 11 with a layer 21 of insulation material between. Wires 22 and 23, for connecting the switch into a desired electrical circuit, are soldered or otherwise secured to the terminal posts 17.

Between the contact terminals, 14 and 15, and on diametrically opposite sides of the aperture 12, there are attached to the plate 11 by nuts 24 and bolts 25 two leaf springs, 26 and 27, which extend past the periphery of said aperture to bear upon the disk 13. The contact bar 28 of conductive material is fixed to the disk 13 by bolts 29 and extends beyond the limits of said disk normally to firmly engage the contact surfaces 16 of the contact ter- 2,772,330 Patented Nov. 27, 1956 ice minals, 14 and 15, thus forming an electrical path between said contact terminals.

As best seen in Fig. 1, the disk 13 is restrained from being displaced from the aperture 12 by the engagement of the contact bar 28 with the contact surfaces 16 of'the contact terminals and by the action of the leaf springs, 26 and 27, in urging said disk and contact bar into engagement with the contact surfaces 16. The strength and tension of the leaf springs 26 and 27 may be varied to calibrate the pressure switch for operation by various magnitudes of force.

In operation, the entire switch assembly is supported in any convenient place exposed to an expected shock wave. For example, when investigating the propagation of shock waves produced by the detonation of an explosive charge, it is desirable to position a plurality of switches at successive distances from the charge. In this manner it is possible to determine the rate of progress of the shock wave from the point of detonation to any predetermined location away from said point. Each switch is so oriented that the leaf springs, 26 and 27, contact terminals, 14 and 15, and contact bar are facing away from the explosive charge. Since both sides of the switch are exposed to the atmosphere, atmospheric pressures will have little tendency to move the disk 13 and thus open the switch. However, when a shock wave from the point of detonation meets the disk 13, the pressure of the wave exerts a force upon said disk to push it against the restraint of the leaf springs 26 and 27 and out of the aperture 12 altogether. Thus the engagement of the contact bar 28 and the contact surfaces 16 of the respective contact terminals 14 and 15 are broken and the switch is opened. It should be understood that the shock wave displaces the springs 26 and 27 and blows the disk 13, carrying the contact bar 28, out of the aperture 12 altogether, thereby completely eliminating any possibility of remaking the circuit.

Inasmuch as the engagement of the contact bar 28 with the contact surfaces 16 is rigid and inflexible, any slight movement of the disk 13 will break the engagement and open the circuit. Therefore, the time of response of a switch embodying this invention is extremely small, e. g. of the order of 22 microseconds. Times of response of this order of magniture are small enough to be neglected in making time interval computations, thereby greatly facilitating the reduction of recorded data.

It is to be emphasized that the present invention is not to be limited in use to experimentation relating to shock wave propagation. A switch having the characteristics described above is applicable to various and sundry uses wherein high sensitivity and short response time are required.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

A sensitive pressure switch comprising, a fiat plate having an aperture formed therein, a disk loosely fitting within said aperture, a pair of contacts oppositely disposed adjacent the periphery of said aperture, a contact bar on said disk and extending beyond the edges thereof for engaging said contacts to complete a circuit therethrough, said bar preventing forward movement of said disk from said aperture, and a pair of spring clips on said plate and engaging said disk near the edge thereof for urging said disk forward and said contact bar into engagement with said contacts, said clips disengaging from said disk upon rearward motion of said disk, whereby a fluid pressure difierential acting upon said disk to cause rear- 3 ward movement thereof will completely displace said disk from said aperture thereby preventing reclosure of the circuit through said contacts.

Wollensak Jan. .5, 1892 Schultz Apr. 3, 1906 4 r Mebold Sept. 17, 1907 Aikman 'Nov.' 11, 1913 Harrison Aug. 25, 1914 Turner M June 1, 1915 Wilhelm Mar. 1, 1927 Allen Mar. 30, 1937 Lindsay June 29, 1937 

